Apparatus for adjusting the elevation of a specimen in microtomes, particularly ultramicrotomes

ABSTRACT

Adjustment of the specimen holder arm with respect to the knife in microtomes and ultramicrotomes is desirable to compensate for eccentrically located specimens in the plastic bedding. Moving the specimen holder arm eccentrically is accomplished by manual movement of the driving means which isolates the specimen holder arm. Preferably, the movement is accomplished through mechanical linkage providing precision control under the movement.

Blum 83/9155 UX Umted States Patent 1191 1111 3,828,641 Sitte 1451 Aug. 13, 1974 APPARATUS FOR ADJUSTING THE 3,191,477 6/1965 Danon 83/9155 x E VATI N OF A SPECIMEN IN ig g PARTICULARLY FOREIGN PATENTS OR APPLICATIONS 238,963 3/1965 Austria 83/9155 ULTRAMICROTOMES 1 238,964 3/1965 Austria 83/9155 [75] Inventor: Hellmuth Sitte, l-Iumburg/Saar, I Gelmany Primary Examiner'-Willie G. Abercrombie [73] Assignee: C. Reichert Optische Werke AG, Attorney, A em, or Firm-Alan l-l. Spencer; William 8 Vienna, Austria C. Nealon [22] Filed: Nov. 10, 1972 [21] Appl. No.: 305,627 ABSTRACT 1 Adjustment of the specimen holder arm with respect [30] Foreign Application Priority Data to the knife in microtomes and ultramicrotomes is de- Nov. 12, 1971 Austria 9764/71 Sirable to compensate for eccemfically located p mens in the plastic bedding. Moving the specimen 52 US. Cl 83/703, 83/410, 83/9155 holder arm eccentrically is accomplished by manual [51] int. Cl .1 B26d 7/06 movement of the driving mans which isolates the [58] Field of Search....; 83/9155, 410, 703 Specimen holder Preferably, the movement is complished through mechanical linkage providing pre- 5 References Cited cision control under the movement.

UNITED STATES PATENTS 1 Claim, 4 Drawing Figures PAIENTED ms t 31924 sum 1 or 2 APPARATUS FOR ADJUSTING THE ELEVATION OF A SPECIMEN IN MICROTOMES, PARTICULARLY ULTRAMICROTOMES BACKGROUND OF THE INVENTION This invention relates to microtomes and more particularly to apparatus for adjusting the elevation of a specimen in microtomes, particularly .ultramicrotomes, in which apparatus the specimen is adjustably disposed at one end of a specimen carrier arm and during the cutting movement moves along a curved or circular path about'a bearing on which the other end of said specimen carrier arm is movably mounted.

In microtomes, particularly ultramicrotomes, the specimen is often moved through a distance in the order of 5-10 millimeters. These small strokes create difficulties if the specimen is eccentrically disposed in plastic material, as is shown by way of example in FIG. 1a, or if an extended specimen is embedded in a thin block and only an eccentrically disposed portion'of the specimen is of interest. Specimens are embedded in most cases in plastic blocks which are 5-8 millimeters in diameter and have been polymerized about the specimen. The eccentricity of the specimens is frequently fl millimeters and the specimen diameter is usually about 1-2 millimeter. Eccentricity cannot be accomodated in many cases by a rotation of the block in the specimen holder because structures having certain directional characteristic must, for known reasons, be cut in proper orientation relative to the knife edge. Whereas it is sometimes possible to adjust the elevation of the knife to an accuracy of about :1 millimeter, e.g., with the aid of a straight-edge which is pivoted with respect to the knife carrier and can be swung up. The factors which have been mentioned above result in deviations of :4 millimeters, of which :2 millimeters are due to eccentricities of the specimen. About 1 millimeter corresponds to one-half diameter of the specimen, and :1 millimeter is due to errors in the adjusted elevation of the knife edge. Larger deviations will arise when larger specimens are trimmed and cut. Cutting speeds of about 0.1 millimeter per second are conventional. If, for the reasons stated above, the cutting range or the vertical movement of the specimen is increasedto millimeters, e.g., in a motor-operated instrument having an adjustable speed drive, a cutting speed of 0.1 millimeter per second will involve a slow movement for 100 seconds. Even if a fast return movement and transition from fast return to the slow cutting stroke are provided, a time of about 1% minutes will elapse between the completionof two successive cuts. This is intolerable, not only due to the working time which is consumed but, there is a very high probability that the accuracy of the sequential cuts is adversely affected by external thermal and mechanical influences. The external thermal and mechanical influences cause problems during prolonged delays between sequential cuts even if temperaturewompensating means are incorporated, even if the instrument is extremely stable dimensionally because all its elements are made from materials having a low coefficient of thermal expansion, and even if the instrument is properly mounted to be shielded as effectively as possible from ambient conditions.

To eliminate these difficulties, the cutting time must be restricted to the minimum essential. For instance, in ultramicrotomes, the minimum movement is of an order between 2 millimeters and 5 millimeters. As has been mentioned above. This involves the difficulty that in case of eccentrically disposedspecimens or of an inaccurately adjusted knife edge elevation, a subsequent vertical adjustment is required. Because errors in the vertical adjustment are generally detected by a check usingan optical instrument, e.g., a stereoscopic microscope, and this check cannot be performed until the cutting operation has begun, the operation must be interrupted at a stage when all other preparations have been made and the specimen'has been moved into engagement with the knife. A. vertical adjustment of the knife can be accomplished best by a vertical displacement of the knife holder or by a vertical adjustment of the specimen resulting from displacement of a part of the specimen carrier arm. It has been discovered that an exact vertical displacement of the knife for a predetermined length and a straight-line displacement of the specimen at right angles to the longitudinal axis of the specimen carrier arm for a predetermined length requires a readjustment at the specimen-knife interface because the specimen moves along an arcuate path during the cut. Therefore, this form of adjustment is complicated and does not give the desired results.

BRIEF DESCRIPTION OF THE INVENTION I It is an object of the invention to provide apparatus which adjusts the elevation of a specimen. It is a further object of the present invention to avoid the disadvantages mentioned hereinbefore and provide a fast and accurate vertical adjustment of the specimen with a corresponding reduction of the cutting time to a minimum. These objects are accomplished by the apparatus of the present invention having the specimen carrier arm adapted to be adjusted in a substantially vertical direction independently of the cutting movement.

With such an arrangement, the elevation of the specimen carrier arm can be adjusted in a simple manner and with a high degree of accuracy for the required specimen detail and there is no need for adjusting movement which adversely affects the precision bearing for the specimen carrier arm. One adjustment of the knife is sufficient and the knife may be used in a single, standardized elevation regardless of the eccentricity of different specimens.

Further advantages and features of the invention will be described hereinafter with reference to an illustra- L e ea qitn atas sh aiat a ia FIG. 1a' shows a specimen which is highly eccentri DETAILED DESCRIPTION OF THE INVENTION According to FIG. 2, the body 1 carries a compound slide 2, on which knife holder 3 provided with an adjusting means 4 is mounted. The body I also carries mount 5, which includes brackets, supports and other rigid elements (all not shown) and on which arm 7 is movably mounted by bearing 6. This bearing is a precision bearing and preferrably is self-adjusting to eliminate conventional bearing clearance. Arm 7 carries the specimen holder 8 in a rotatable mount 9, which is manually adjustable along an arcuate segment member 10. The specimen 11, embedded in a conventional manner such as in plastic, is gripped by specimen holder 8. The feeding system, not shown. is conventional and provides for cutting sections having a thickness in the range from 0.05-2.5 microns. Conventional feeding systems may be mechanically or thermally operated or may be combined mechanical-thermal system and the feedingmovement. may be imparted, to the specimen carrier arm, to knife 26 or both. As shown, motion is transferred to specimen 11 by eccentric cam, or the like, v13 mounted on drive shaft 12 and link 14 driven by eccentric l3'at one end and detachably pivoted carrier arm 7 at the other end. Rotation of drive shaft 12 results in an up and down alternate motion of the link 14 and of arm 7 in the direction of double arrows 15 and-16a, respectively. For known obvious reasons, this movement should be minimized so that the optimum cutting speed of the specimen for making the sections is ensured with a relatively high cutting frequency and a relatively high angular speed of the drive shaft. Frequently, the optimum cutting speeds are within a range of 0.1-2 millimeters per second, as has been mentioned above. Specimens which can be cut only with difficulty, such as adipose tissues, require extremely low cutting speeds for example. When such specimens are cut at high speeds, the cut may result in artefacts or produces microvibrations at the specimenknife interface, resulting in undulations in the ultrathin section.

' In a preferred embodiment of the present invention, the drive shaft 12 is rotatably supported by housing 16, which can be moved in the direction of the double arrow 16a. An adjusting device utilizing convention components such as a transmission comprising a wedge-shaped camwheel, or of a worm gearing is used to position housing 16. A particularly simple arrangement is illustrated using bevel gears 17 and 18. Bevel gear 17 is mounted on shaft 19, which can be manually rotated by knob 20. Bevel gears 17 and 18 may be designed to be self-locking, or the knob 20 may be releasably secured from rotation, for example by clamping, to provide adjustment which is maintained during operatlon.

Housing 16, in which the drive shaft 12 is mounted, is adapted to be supported by a carrier member 21 recounted on body 1 of the instrument. To eliminate inaccuracy, for instance, at the bearings, joints and the like, a spring 22 is provided, which at one end is connected to body 1 and at the other end is connected to housing 16. This arrangement ensures that the means for a vertical adjustment have a stable mounting, will reliably respond to any forces, will transmit even the slightest adjusting movement to arm 7, and also ensures that any adjustment, e.g., to an eccentricity e as shown in FIG. 1, may be effected and maintained without any backlash.

Housing 16 is also provided with an indicator 23, which has scales or graduations and which is indirectly connected to the link 14 and indicates corresponding motion of the link. Body 1 is provided with mask 24, which is formed with an aperture located adjacent to graduations or scales of indicator 23. The position indicator behind the mask reveals the vertical setting of arm 7 as well as the changes in the position. Instead of mask 24, the aperture may be in'a housing wall, not shown. in this case, the scale or graduation is provided on the outside of the housing wall. Through the combination of mask and indicator, the relation of the absolute elevation of the arm 7 to a reference mark as well as the adjusted eccentricity are indicated and the exact position is indicated. Operation of knob 20, rotates screw 25 having fine threads by means of the bevel gears 17 and 18. Rotation moves the housing 16 in one of the directions indicated by double arrow 16a. Knob 20 may have adjustable graduations or scales (not shown) so that a predetermined vertical adjustment can be imparted to housing 16. The graduations may be designed as a distance measuring graduation so that specific adjustment can be rapidly effected to position a specimen at a particular setting.

FIG. 3 shows a modified, very compact embodiment of the apparatus according to the present invention. This embodiment is combined with a drive motor, which is disposed outside the microtome or ultramicrotome.

A substantially horizontally extending level 29 is rotatably or pivotally mounted by bearing 28 and near its other end cooperates with drive shaft 12. The up and down alternate movement of the arm 7 is accomplished by means of the eccentric 13 mounted on drive shaft 12, and link 14. The elevation of the specimen 1 l is adjusted by knob or handwheel 30, and which by means of a shaft 31 rotates the cam 32 -so that follower 33 causes level 29 to be pivotally moved about the bearing 28 in the direction of the double arrow 34. Knob 30 is provided with at least one graduation or scale 35 and can be releasably secured in position by clamping. The stressed spring 22 holds cam 32 in engagement with follower 33 to eliminate backlash.

It is advantageous not to couple the driving motor directly to the drive shaft 12, as mentioned above, but rather to provide transmission 37 between the driving motor 36 and a double belt pulley 38, which is coaxially and rotatably mounted relative to the bearing 28 or directly mounted in the same. Pulley 38 is connected by at least one transmission belt 39-to pulley 40, which is fixed drive shaft 12.

The separation of the driving motor from the microtome or ultramicrotome affords the advantage that shocks and vibrations will be absorbed by the drive means and the belts and are not transmitted to the instrument. This will be particularly significant if the alternate motion is rapid. it is also possible to mount the microtome or ultramicrotome on a specially designed stand, which damps vibration, and to mount the motor separately so that the two are connected only by the flexible belt.

A tension member 41 is arranged around the axis of bearing 28 and operates the feed drive, not shown, as well as the means for retracting the specimen for return movement. Tension member 41 is secured to a control 43, which is movable about axis 42 and which, in response to rotation of the drive wheel 12 and cam 44 moves in the direction of the double arrow 45 to operate the feed movement.

Numerous modifications are possible within the scope of the invention. For instance, it is not essential that the means for adjusting the specimen carrier be de signed and arranged as specifically shown, although drive means, a rotatable externally threaded shaft adapted to cooperate with an internally threaded passage to move said positioning means upon rotation of said shaft to provide adjustment of the position of said arm with respect to said knife to accommodate eccentricity of the specimen in the plastic, said positioning means carrying a graduated scale to indicate the relative position of said arm with respect to said knife. and a graduated cylindrical scale connected to said shaft to provide visual means indicating the distance the arm is moved. 

1. A microtome for cutting specimens mounted in plastic comprising a body, a knife adjustably mounted on said body, an arm pivotably mounted at one end to said body, a specimen holder adjustably mounted at the other end of said arm adjacent said knife, drive means adapted to oscillate said arm, positioning means slidably mounted on said body and adapted to carry said drive means, a rotatable externally threaded shaft adapted to cooperate with an internally threaded passage to move said positioning means upon rotation of said shaft to provide adjustment of the position of said arm with respect to said knife to accommodate eccentricity of the specimen in the plastic, said positioning means carrying a graduated scale to indicate the relative position of said arm with respect to said knife, and a graduated cylindrical scale connected to said shaft to provide visual means indicating the distance the arm is moved. 